Book
Categories:
Fundamental Ephemeris Computations
332 Pages, Hardbound,
6 by 9 inches
Includes Source on CDROM Power BASIC & C
$29.95
Fundamental
Ephemeris Computations: For Use with JPL Data, Includes C and PowerBasic Source
Code on CDROM
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About
This Book:
Within the last decade there have been many books
dealing with the application of personal computers to general problems in
celestial mechanics. So, the reader may ask, Why one more? The most evident
reason is the use of approximations. Usually a full verbal explanation of a
procedure is given, but when the algorithm is programmed, approximations are
often made that, in the final analysis, defeat the power of a computer. Modern
microcomputers are wonderful machines, never tiring of performing the same
computations over and over again until the user is satisfied with the result.
While it is true that efficient coding often reduces the execution time, the
point is that there is no need to make any great approximations until the very
end of the computation. For instance, it is generally accepted that it is
useless to compute times of sunrise and sunset to an accuracy greater than one
minute of time because of the uncertain nature of atmospheric refraction near
the horizon and the constantly changing local meteorological conditions.
However, why not let the computer perform the computation to the full precision
of the machine and then let the user round the result to the nearest minute of
time?
Another major problem with existing computer-oriented
astronomical books is that there has been little or no effort to adopt the
computational algorithms used for the preparation of data in the national
almanacs, particularly the U.S. Naval Observatorys Astronomical Almanac. So the
primary goal of this book is to present a library of useful PowerBASIC and C
subprograms and functions that can be combined to make powerful application
programs. These routines cover both elementary and advanced topics in
computational celestial mechanics and spherical astronomy such as time systems,
precession, nutation, coordinate transformations, orbital elements and
ephemerides, reduction to apparent place, rise/transit/set times for celestial
objects, and use of the JPL ephemerides. Care has been taken to present the
results of computations in the same form as the corresponding data in the
Astronomical Almanac and at least to the same precision. This book is the only
one describing how to obtain, process, and use the official Jet Propulsion
Laboratory ephemeris data files. The JPL ephemerides form the basis of
practically all of the national astronomical almanacs, including the
Astronomical Almanac. Many readers will be surprised to learn that these data
files are available free from JPL via the Internet or via a CD-ROM prepared by
JPL and published by Willmann-Bell ( $24.95 plus $1.00 shipping).
See sidebar for details about the JPL CD-ROM. In this book the author gives
explicit instructions on how to retrieve them from JPL and put them into a
usable form. In addition, with this book comes a disk that includes enhanced
PowerBASIC and C versions of the original JPL FORTRAN processing software that
manipulates the data files. Today, these ephemerides are considered to be the
final word on planetary ephemerides, and now the serious non-professional who
wants to make use of them can do so.
Table of Contents
Preface
iii
1 Introduction 1
1.1 What is a Fundamental Ephemeris?
1.2 The
Software Source Code
1.2.1 Program Requirements
The BASIC Code
The
C Code
1.2.2 Modifying the Source Code
1.2.3 Programming
Conventions
2 Astronomical Time Systems
2.1 Introduction
2.2 The
Various Time Scales
2.2.1 Dynamical Time
2.2.2 Barycentric Dynamical
Time
2.2.3 Atomic Time
2.2.4 Terrestrial Dynamical Time
2.2.5
Sidereal Time
2.2.6 Universal Time
2.2.7 Ephemeris Time
2.2.8
Barycentric Coordinate Time
2.3 Relationships Between the Time Scales
2.4 Julian Day Numbers and Calendar Dates
2.5 More On Sidereal Time
3
Precession and Nutation
3.1 Introduction
3.2 Obliquity of the
Ecliptic
3.3 Precession
3.4 Nutation
4 Coordinate Systems and
Transformations
4.1 Introduction
4.2 Preliminary Explanations
4.3
The Astronomical Coordinate Systems
4.3.1 The Horizon System
4.3.2 The
Equatorial System
4.3.3 The Ecliptic System
4.3.4 The Observers
Geocentric System
4.4 Transformation from One Coordinate System to
Another
5 Orbital Elements and Ephemerides
5.1 Introduction
5.2
General Orbital Elements
5.3 Elliptical Orbits
5.4 Hyperbolic
Orbits
5.5 Parabolic Orbits
5.6 Treatment with Universal Variables
5.7 Conversion from State Vector to Orbital Elements
5.8 Precession and
Orbital Elements
6 Position Reductions for Celestial Object
6.1
Introduction
6.2 Preliminary Explanations
6.2.1 Mean Place
6.2.2
Apparent Place
6.2.3 Topocentric Place
6.2.4 Virtual Place
6.2.5
Local Place
6.2.6 Astrometric Place
6.3 Apparent Place of Major
Planets
6.4 Apparent Place of Stellar Objects
6.5 Atmospheric
Refraction
7 Rise, Transit, and Set Times
7.1 Introduction
7.2
Explanatory Notes
7.3 Subprogram for Computing Rise/Transit/Set Times
8
Sources of Fundamental Ephemerides
8.1 Introduction
8.2 Origin of the
Data Files
8.3 Obtaining the Ephemeris Data Files
8.4 Processing the
ASCII Data Files
8.5 Identifying a Binary Data File
8.6 Using the
Binary Data Files
8.6.1 EPHOPN
8.6.2 CONST
8.6.3 PLEPH
8.6.4
STATE
8.7 Header File Format
9 Numerical Methods
9.1
Introduction
9.2 Utility Functions
9.3 Interpolation
9.4
Trigonometry Routines
9.5 Matrix and Vector Methods
9.6 Generalized
Matrix Methods
10 A Command Line Ephemeris Program
10.1 Introduction
10.2 Bringing It All Together
10.3 Enhancing SEPHEM
Appendix A C
Source Code
Bibliography
Index
About the
Author
With degrees in
both astronomy and physics, Joe Heafner teaches these subjects at Catawba
Valley Community College in Hickory, North Carolina and occasionally teaches
introductory astronomy at UNC-Charlotte. An active member of the Catawba Valley
Astronomy Club, Joe enjoys stargazing of all kinds, giving children their first
view of Saturns rings through a telescope, and collecting rare mathematical
astronomy and celestial mechanics books. Joe is a member of the American
Astronomical Society and the American Association of Physics Teachers. This is
his first book.
JPL Planetary
and LunarEphemerides on CD-ROM, Standish et al.
CD-ROM,
1 lb. ship wt.
$24.95
This CD contains three Jet Propulsion Laboratory Planetary and Lunar Ephemerides
along with associated reading and interpolating routines. These allow
a competent programmer to obtain the rectangular coordinates of the sun,
moon, and nine major planets by means of a subroutine written in standard
Fortran. DE200: (includes nutations but not librations) JED 2305424.5
(1599 DEC 09) to JED 2513360.5 (2169 MAR 31). This ephemeris has been
the basis of the Astronomical Almanac since 1984. It is based upon the
dynamical equator and equinox of J2000. DE405: (includes both nutations
and librations) JED 2305424.50 (1599 DEC 09) to JED 2525008.50 (2201 FEB
20). JPLs latest ephemeris, created in May-June, 1997. DE405 is based
upon the International Celestial Reference Frame (ICRF), the newly-adopted
reference frame of the International Astronomical Union (IAU). The frames
of DE200 and DE405 differ by no more than about 0.01 arcseconds. DE406:
the New JPL Long Ephemeris (includes neither nutations nor librations)
JED 0625360.50 (3000 FEB 23) to 2816912.50 (+3000 MAY 06). DE406 is the
same ephemeris as DE405, though the accuracy of the interpolating polynomials
has been lessened (interpolation on the 64-day mesh points remains exact,
however). For DE406/LE406, the interpolating accuracy is no worse than
25 meters for any planet and no worse than 1 meter for the moon.
Third Party Resources to the JPL CDROM (PDF)